PROJECT SUMMARY/ABSTRACT Toll-like receptor and respiratory microbiota interactions in pulmonary fibrosis Idiopathic pulmonary fibrosis (IPF) is a lethal disease with no known cure, unknown etiology and poorly understood pathogenesis. It is an emerging global health issue with an estimated 5 million people affected worldwide and 17,000 deaths in the United States annually. The advent of culture-independent microbial identification techniques has identified a respiratory microbiome associated with several lung diseases. Novel clinical observations using bronchoalveolar lavage (BAL) fluid from IPF patients support a role for the respiratory microbiome, both changes in community members and overall burden (dysbiosis) in disease progression and mortality. Innate immune mediators including Toll-like receptors (TLR) have reported associations with clinical outcomes in IPF, highlighting the previously underappreciated role of host defense in IPF pathogenesis. However, the precise role of the respiratory microbiome and host interaction in pulmonary fibrosis is poorly understood. The central hypothesis of this project is that dysbiosis promotes progressive lung fibrosis through stimulation of TLRs to modulate cell-specific fibrotic responses. The specific objective is to employ techniques from microbial ecology, bioinformatics, cell biology and animal modeling (including germ free and gnotobiotic models) to determine the role of dysbiosis in regulating lung pathophysiology in pulmonary fibrosis. The long term goal is to understand the role of host-microbiota interactions in the pathogenesis of IPF and design specific therapeutic strategies for patients based on an improved understanding. In order to achieve this objective, established animal models of pulmonary fibrosis in germ free and conventional mice with or without antibiotic manipulation of the microbiota will be studied initially to understand the role of dysbiosis, the host innate immune and defense response and to identify microbes associated with experimental pulmonary fibrosis to guide gnotobiotic studies. Subsequent studies of experimental fibrosis in animal models deficient in TLRs associated with the recognition of Gram positive (Toll-like receptor 2) and Gram negative bacteria (Toll-like receptor 4) will further define microbiota-host interactions. Dr. O?Dwyer has experience in TLR signaling and fibrosis and has previously published in this area. His career development plan is focused on further mentored training in animal modeling and the bioinformatics of microbial ecology. This project will be undertaken within the University of Michigan?s Medical School through the Department of Internal Medicine, Department of Microbiology and Immunology and the University?s Host Microbiome Initiative. These state-of-the-art studies will identify candidate organisms associated with fibrosis, characterize microbiota-host (TLR) interactions that drive fibrogenesis and will highlight the crucial role that dysbiosis plays in the pathogenesis of lung fibrosis to advance our understanding of disease etiology, refine current animal models and inform new therapeutic strategies for this devastating lung disorder.